I haven't heard about this.
I'd open a support ticket incl. a backup for Kemper to try if they can replicate the issue.
This may sound obvious, but did you by any chance tweaked the rig in the performance? This is a different physical file, so they may sound different from each other if you changed anything at some stage
I got an idea:
You say: 'The very same rig sounds much brighter when i switch to perform mode'.
But do you know that when you change to PM you never hear the same rig?
You hear a rig in a slot in a performance, but not the rig you had previously in browse mode.
What you need to do to check:
Choose a performance, poulate one slot with the rig from browse mode that you think sounds different, incl. same FX and make sure input sens is the same (because it can be different in BM and PM).
Now you can switch back and forth. Still different?
To make a test, i selected the first rig on the BM and placed it on an empty slot on the PM. The EQ was completely different when i A/B'd the two modes. Then i pressed the stack button for 2 secs to copy everything from the rig in the BM. Pasted it on the stack of the PM rig. Boom! They sound the same. Maybe i've dialed in an EQ setting and locked it so every rig i take into the PM is effected by that EQ setting. I donT know. All I know is now I have to do that copy/paste thing for all the rigs i have on the PM. 
@viabcroce yes i checked that by choosing a different rig and taking that into the PM without dialing any EQ or else.
@Ingolf the sense settings are all set to 0.0 dB on both modes.
Sorry guys. I'm a fool! When I checked the details on the stack elements I saw that i've locked the cab on the PM mode. Maybe it's ridiculous but people can read this thread and realise that we can get lost in small details 
I've done that before. Definitely need to be careful what you lock. If you weren't already aware, you can see exactly what's locked by holding the lock button in browse mode. I've found this helpful a lot.
Yeah it had to be something along those lines...
Good that the culprit is identified. 
... The point I was missing is that you can lock things differently in BM and PM.
Good to know, thanks!
Do you guys like the ability to lock different things separately in Browse and Performance mode?
I think is a powerful option, as long as the user drops the mindset that he's using "the same rig" in a performance. Appreciating this feature implies IMO to start considering a performance like an echosystem on its own, which I'm starting doing as long as I deepen the Performance mode.
Is this documented anywhere, BTW?
Sounds like a great idea CK
*edit: Wait...is this already a thing??
It's great to lock different things in BM and PM.
Absolutely like it, although I must confess that sometimes I forget and I'm not sure exactly what can we locked independently. Is there a list….or is it as simple as "everything"?
Do you guys like the ability to lock different things separately in Browse and Performance mode?
Do you guys like the ability to lock different things separately in Browse and Performance mode?
It's useful. That's for sure. Unless you don't forget what you lock!
